For convenience purposes, it is well known to provide garage doors which utilize a motor to provide opening and closing movements of the door. Motors may also be coupled with other types of movable barriers such as gates, windows, retractable overhangs and the like. An operator is employed to control the motor and related functions with respect to the door. The operator receives command signals for the purpose of opening and closing the door from a wireless remote, from a wired wall station or other similar device. It is also known to provide safety devices that are connected to the operator for the purpose of detecting an obstruction so that the operator may then take corrective action with the motor to avoid entrapment of the obstruction.
To assist in moving the garage door or movable barrier between limit positions, it is well known to use a remote radio frequency or infrared transmitter to actuate the motor and move the door in the desired direction. These remote devices allow for users to open and close garage doors without having to get out of their car. These remote devices may also be provided with additional features such as the ability to control multiple doors, lights associated with the doors, and other security features. As is well documented in the art, the remote devices and operators may be provided with codes that change after every operation cycle so as to make it virtually impossible to “steal” a code and use it a later time for illegal purposes. An operation cycle may include opening and closing of the barrier, turning on and off a light that is connected to the operator and so on.
In order for a remote controlled device to work with an operator to control movement of the garage door, the operator must be programmed to learn the particular code for each transmitter. In the past, radio controls utilized a code setable switch, such as a ten-circuit DIP switch to set the data for both the transmitter and the receiver. Both the transmitter and the receiver's code switch would have to match for the transmitter to activate the receiver's output. This method did not allow for enough unique codes and was relatively easy for someone to copy the code and gain improper access. Accordingly, this process requires the setting of transmitter and receiver codes physically switched to identical settings for operation of the garage door.
Presently, most radio controls for garage doors use either a fixed code format wherein the same data for each transmission is sent, or a rolling-code format, wherein some or all of the data changes for each transmission. A fixed code transmitter, also known as a fixed address or a fixed serial number transmitter, is assigned and factory programmed into a transmitter's non-volatile memory during the manufacturing of the product. A receiver is designed to “learn” a transmitter's code and the transmitter's code is stored in the receiver's non-volatile memory. This increased the number of possible codes (from 1024 or 19,683 to millions) and eliminated the DIP switch. This also prevented the code from being visible, as is the case with the DIP switch transmitter, thus preventing theft of the code. But, shortcomings for using a fixed code are that a transmitter's code can still be stolen electronically by having a nearby transceiver (transmitter and receiver built as one) receive the valid transmitter's code then, at a later time, resending the code to activate the receiver. And it is still possible to make a transmitter that increments through all possible fixed codes to activate the receiver. Since the number of codes is greater than a DIP switch system, the time needed to step through every possible code greatly increases. But, the possibility of theft remains.
A rolling code transmitter is similar to a fixed code transmitter, but at least a portion of the address, also known as the code or serial number, is changed with every operation of the transmitter. The transmitter and the corresponding receiving unit use an algorithm to determine what the next code to transmit/receive shall be. In other words, the serial number portion of each rolling code transmission always remains the same. And the algorithm, sing the serial number, anticipates what the next rolling code transmission should be. Only the proper code will activate the receiver. Shortcomings of both devices are that once the transmitter is programmed at the factory during its assembly, a user cannot change the transmitter's code or serial number.
Such an exemplary rolling code system is disclosed in U.S. Pat. No. RE 36,703 which describes a system for remote control of garage doors and other movable barriers. The disclosed system uses an extremely large number of codes for a remote transmitter enabling the operator, wherein each transmitter has its own unique and permanent non-user changeable code or serial number. The operator includes a receiver that is capable of learning and storing codes for different transmitters such that the receiver can be actuated by more than one transmitted code, thus allowing two or more transmitters to actuate the same garage door. Although an improvement in the art, the aforementioned system is deficient in that the configuration of the transmitter can never be changed. In other words, one cannot automatically “un-learn” a transmitter for operating a receiver. Another exemplary rolling code system is disclosed in U.S. Pat. No. 6,049,289, which sets out a remote control system for opening and closing a garage door barrier and includes a radio frequency (RF) receiver and a plurality of RF transmitters. The transmitters and receiver are configured to use encrypted code signals each time the transmitters are used and employ a code hopping method which prevents unauthorized signal interception or code “grabbing.” Each transmitter is initially programmed with a unique serial number and a unique “secret key.” The secret key stored in the transmitter is generated using the unique serial number in the transmitter and the manufacturer's key. Every transmitter has a different serial number and a different secret key. When the transmitter is activated, it performs a nonlinear encoding function using the secret key to generate a changeable hopping code signal. In other words, the hopping code changes every time the transmitter is activated. The transmitter's unique secret key is never transmitted and although the transmitter's unique serial number is transmitted, it is not stored in the receiver. Each transmitter is initially programmed with the following: (a) a 24-bit serial number, (b) a 64-bit secret key, (c) a check value, and (d) an initial synchronization value.” The unique serial number is also directly stored in the transmitter 40 and the 24-bit serial number is unique to each particular transmitter 40 and is then stored in the transmitter during initial programming and does not change from one transmission to the next. Accordingly, although the hopping code changes for each transmission, it is clear that this patent teaches that the serial number remains the same for each transmission. In other words, when a transmitter is activated, the serial number and the hopping code, which is derived from the secret key, is transmitted. Accordingly, the hopping codes changes with each transmission, but the serial number always stays the same.
Therefore, a need exists for transmitters that allow for the user to change the transmitter's serial number. There is also a need to have a transmitter that has a simple first time change serial number operation and a more complex serial number change operation for subsequent serial number changes.